Effects of surface finishing procedures on the color, gloss, and surface roughness of CAD/CAM ceramics after coffee aging: an in vitro study surface finishing effects on CAD/CAM ceramics

Aims: This in vitro study aimed to evaluate the effects of different surface finishing procedures-mechanical polishing, glazing, and polishing followed by glazing-on the color stability, surface roughness, and gloss of three CAD/CAM ceramic materials [feldspathic glass ceramic (GC), lithium disilicate (LDS), and zirconia-reinforced lithium silicate (ZLS)] after aging in a coffee solution. Methods: A total of 108 rectangular ceramic specimens (n=36 per material) were prepared in accordance with ISO 6872. Each material was divided into three subgroups based on the surface finishing procedure: mechanical polishing, glazing, and polishing+glazing. Baseline measurements of surface roughness (Ra), gloss (GU), and color (CIEDE2000, ΔE₀₀) were recorded. Specimens were aged in a coffee solution at 37 °C, and measurements were repeated at 1 week, 2 weeks, 1 month, and 2 months. At the end of the 2-month period, all specimens were re-polished and final measurements were obtained. Data were analyzed to determine material-, time-, and procedure-dependent differences. Results: Surface finishing protocols significantly affected all evaluated parameters (p < 0.05). Mechanical polishing produced the lowest Ra values (0.19±0.05 µm), while glazing alone resulted in the highest Ra after aging. The greatest increase in Ra was observed in zirconia-reinforced lithium silicate, whereas LDS maintained the lowest values throughout the study. The polishing+glazing protocol exhibited the highest GU (76.24±9.19 GU). LDS ceramic demonstrated the best GU retention, while ZLS showed the most pronounced loss over time. Both material type and finishing method significantly influenced ΔE₀₀ (p